title: Characterization of a cryptic plasmid from an alpha-proteobacterial endosymbiont of Amoeba proteus.
abstract: A new cryptic plasmid pAP3.9 was discovered in symbiotic alpha-proteobacteria present in the cytoplasm of Amoeba proteus. The plasmid is 3869bp with a GC content of 34.66% and contains replication origins for both double-strand (dso) and single-strand (sso). It has three putative ORFs encoding Mob, Rep and phosphoglycolate phosphatase (PGPase). The pAP3.9 plasmid appears to propagate by the conjugative rolling-circle replication (RCR), since it contains all required factors such as Rep, sso and dso. Mob and Rep showed highest similarities to those of the cryptic plasmid pBMYdx in Bacillus mycoides. The PGPase was homologous to that of Bacillus cereus and formed a clade with those of Bacillus sp. in molecular phylogeny. These results imply that the pAP3.9 plasmid evolved by the passage through Bacillus species. We hypothesize that the plasmid-encoded PGPase may have contributed to the establishment of bacterial symbiosis within the hostile environment of amoeba cytoplasm.
authors.affiliation: Department of Biological Science, Seoul National University, Kwanak-Gu, Seoul 151-742, Republic of Korea.
authors.forename: Miey
authors.initials: M
authors.lastname: Park
authors.forename: Min-Soo
authors.initials: MS
authors.lastname: Kim
authors.forename: Kyung-Min
authors.initials: KM
authors.lastname: Lee
authors.forename: Sue-Yun
authors.initials: SY
authors.lastname: Hwang
authors.forename: Tae In
authors.initials: TI
authors.lastname: Ahn
mesh_terms: D020561:Alphaproteobacteria / Q000235:genetics* / Q000502:physiology; D000595:Amino Acid Sequence; D000656:Amoeba / Q000382:microbiology*; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics; D001483:Base Sequence; D004269:DNA, Bacterial / Q000235:genetics; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D010957:Plasmids / Q000235:genetics* / Q000302:isolation & purification; D016415:Sequence Alignment; D013559:Symbiosis
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; C083180:Mob protein, Bacteria; C022408:phosphoglycolate phosphatase; D010744:Phosphoric Monoester Hydrolases